Low-level laser therapy (LLLT) has a non-thermal, biostimulative effect on biological tissues and produces beneficial clinical effects in the treatment of musculoskeletal, neurological and soft tissue conditions. LLLT delivers light energy photons, penetrating the layers of skin and reaching targeted internal tissues to produce a specific, non-thermal photochemical effect at the cellular level. (1) Some of the known effects of LLLT include the enhancement of ATP production, which acts as the trigger for the biostimulating effect,(2) improved microcirculation and bone regeneration, (3) and accelerated wound healing in human sports injuries and accidents.(4)
A method currently used to accelerate the wound healing process is hyperbaric therapy. But this does not always work, and is particularly a problem for the elderly, bedridden and others with slow healing processes. However, the enhancing effect of LLT on microcirculation and wound healing (3) (4) is likely to aid in treatment by accelerating the regenerative process of the tissues.
A 74-year-old male presented with a non-healing diabetic wound on the right heel at the insertion of the Achilles tendon into the calcaneous. The wound had been active for six months and the patient reported to have just finished 65 sessions of hyperbarbic therapy, with no response. The patient used a special brace on his right leg to aid in walking. Four years previously, the patient's left leg had been amputated five inches below the knee.
The concern was that if the wound continued to be active it would erode the Achilles tendon at its insertion, and consequently the leg would have to be amputated at the end of the month.
After 12 laser treatments had been administered in one month, the patient's neurosurgeon was pleased with a decrease in the active inflammatory process and an initial regeneration of new muscle tissue. Amputation was delayed for a month.
At the end of the second month, the active inflammatory process was further decreased and regenerated muscle tissue had filled in the cavities, which were present. Surgery was cancelled.
By the end of the third month, the patient began to walk using a regular running shoe.
Continued therapy was geared to healing a small area at the lateral aspect of the Achilles tendon at its insertion into the calcaneous, and to then strengthen the tendon and tissues in the area.
Revascularization is one of the most important stages of wound healing.
The laser (5)(6) has been shown to be very effective in initiating revascularization in injured tissue and increased blood flow. (7) More fundamental features of laser's effect on tissue and wound healing have also been shown to occur. Whelan (8) identified that certain tissue regenerating genes could be manipulated to greatly enhance the natural would healing process.
Cultured human keratinocytes, endothelial cells and fibroblasts, when exposed to laser, caused the production of transforming growth factor, (9) and laser increases the transforming of fibroblasts into myofibroblasts. This is a very important step in wound healing, because the myofibroblasts have filaments which enable them to contract and shrink the wound, (10) and laser decreases the inflammatory process, (11) reducing edema reduction and enhancing lymph flow. (12)
Irradiation of 3 and 4 J/cm2 increased cell numbers about threefold to sixfold compared to control cultures. The energy density of 3 J/cm2 remarkably increased cell growth, with no effect on procollagen synthesis, as demonstrated by immunoprecipitation analysis. (13) Infrared laser radiation (frequency 500 Hz) was more potent in stimulating repair of skin wounds than 300 Hz radiation. (14) Also, the type of laser used contributes significantly to the healing effects,as shown by Zeinoun.(15) He found that there were clearly fewer myofibroblasts when a CO2 laser was used compared to corresponding scalpel excisions known to heal by contraction. The lack of contractile myofibroblasts, therefore, is suggested as the reason for the minimal degree of contraction in CO2 laser excision wounds.
The strength of the wound is also affected by the application of LLLT. With low-power laser irradiation at 830 mm, applied daily over 0-4 days and 3-7 days, it was found at 11 or 23 days post-treatment that the tensile strengths of wounds were significantly enhanced in a murine diabetic model. (16) Reddy (17) showed that after 14 days of laser treatment to the repairing Achilles tendons of rabbits, when the tendons were subjected to biochemical analyses they revealed a 26 precent increase in collagen concentration in the laser photostimulation group, indicating a more reapid healing process in treated tendons compared to controls.
When the repairing medial collateral ligaments (MCL) of rats were exposed to a single high dose of laser therapy, this resulted in increase of the collagen fibril diameters, when comparing experimental and control groups. (18) This would explain why a single dose of low-energy laser therapy improves the tensile strength and stiffness of repairing MCL at three and six weeks after injury. (19)
The laser protocol was instituted after conventional management protocols were shown to be ineffective. The rate and quality of healing of these previously refractory wounds following use of infrared laser energy may be related to local increases in nitric oxide oxide concentration. Increases in nitric oxide previously have been demonstrated to correlate with vasodilatory and anabolic responses. (20)
From case history results and the references cited, laser therapy is seen as beneficial in enhancing the healing of wounds. However, more research is needed to understand the effects of each specific laser parameter, so that improved efficacy can be achieved for the patient.
The above information should provide food for thought for the chiropractic profession. On a daily basis, for example, we treat chronic back pain patients. What percentage of these patients have pathologies in their deep spinal muscles, such as the multifidus muscles? Would pathologies in the muscles benefit from a course of laser therapy? If so, could this improve the efficacy of our manipulative intervention?
These and other questions need to be addressed as the profession accepts the challenges of providing more cost-effective health care to the public.